Over the last several years and particularly since September 11, there has been a significant increase in the number of intrusions into various security zones as well as acts of international terrorism. Although a large amount of time, effort and money has been budgeted to agencies like the Department of Homeland Security, these intrusions and attempts to protect individuals as well as property have not lessened the threat.
Access control devices supervise access at perimeter doors of a facility, but fail to detect vandalism or terrorist threats to the exterior of the facility and the immediate vicinity of a structure or area to be protected.
Existing perimeter security systems and the prior art consist of CCTV cameras, sense cables either buried or attached to metal fences, infrared (IR) and microwave sensors. Limitations are the rule since CCTV cameras are less effective at night and both IR sensors and CCTV cameras are compromised by fog and rain. Furthermore, IR and microwave sensors do not locate the point of the attempted intrusion and fence cables are limited to the use with metal fences. Buried cable sensors require significant site engineering. None of the present solutions can locate intrusions accurately on hard surfaces such as brick walls or buildings.
Vibration based systems often result in false-positive alarms due to trucks traveling on nearby roads, weather, lightening, sonic booms from military aircraft, vibrations from trees/shrubs and animals as well as earthquakes, tremors, seismic rumblings and explosions. Repair and maintenance are frequent and costly. Sophisticated software requiring complicated algorithms must also be developed to determine the approximate location of an alarm.
U.S. Pat. No. 7,069,160 overcomes the shortcomings of the older technologies by utilizing radio frequency identification (RFID) passive proximity microchips to precisely locate intrusions regardless of weather or of the structural material it is attached to or imbedded in. However, this patent includes a power transmission cable that broadcasts an RF UHF signal and a data transmission cable with transponder microchips connected by a data bus that are powered by the transmission cable via electromagnetic coupling. Therefore, an intrusion is sensed by interference in the ability of the transponders to receive the EM field by an individual entering the field. Hydrogen absorption inhibits the EM field by an individual entering the field, and the transponder(s) fail to communicate their encrypted code down the data bus.